Department of Chemistry, Hobart and William Smith Colleges, Geneva, New York 14456, USA.
J Phys Chem A. 2011 Oct 13;115(40):11001-7. doi: 10.1021/jp207383b. Epub 2011 Sep 20.
We describe three new strategies for determining heterogeneous reaction rates using photomicroscopy to measure the rate of retreat of metal surfaces: (i) spheres in a stirred solution, (ii) microscopic powder in an unstirred solution, and (iii) spheres on a rotating shaft. The strategies are applied to indium-mediated allylation (IMA), which is a powerful tool for synthetic chemists because of its stereoselectivity, broad applicability, and high yields. The rate-limiting step of IMA, reaction of allyl halides at indium metal surfaces, is shown to be fast, with a minimum value of the heterogeneous rate constant of 1 × 10(-2) cm/s, an order of magnitude faster than the previously determined minimum value. The strategies described here can be applied to any reaction in which the surface is retreating or advancing, thereby broadening the applicability of photomicroscopy to measuring heterogeneous reaction kinetics.
我们描述了三种使用显微镜测量金属表面后退速率的新策略，以确定非均相反应速率：（i）搅拌溶液中的球体，（ii）非搅拌溶液中的微观粉末，以及（iii）旋转轴上的球体。这些策略适用于铟介导的烯丙基化反应（IMA），由于其立体选择性、广泛的适用性和高收率，它是合成化学家的有力工具。IMA 的速率限制步骤是卤代烯丙基在铟金属表面的反应，该步骤被证明是快速的，非均相速率常数的最小值为 1×10(-2)cm/s，比以前确定的最小值快一个数量级。这里描述的策略可以应用于任何表面在后退或前进的反应中，从而拓宽了显微镜测量非均相反应动力学的适用性。
